1. Field of the Invention
The present invention relates to a slit nozzle comprising left and right portions made of different materials, and an apparatus for supplying a treatment liquid using the slit nozzle.
2. Description of Background Art
Conventionally, there has been known a slit nozzle in which an opening of a predetermined width for ejecting a coating liquid is provided, and the nozzle is moved relatively with respect to an object to be treated so as to apply a coating liquid to the object to be treated in a predetermined width. With the slit nozzle having an opening of a predetermined width, it is possible to apply a coating liquid efficiently without wasting the coating liquid.
However, as an object to be treated becomes large, a single slit nozzle has limits with respect to the time and the amount of supplying a coating liquid. For example, if it takes too much time from the start of supplying a coating liquid to the finish, non-uniformity undesirably occurs. This problem occurs when a coating liquid is supplied so as to form a thick coating.
In order to supply a coating liquid so as to form a thick coating, Document 1 has disclosed that a coating liquid is applied to an object to be coated two times by using two application heads (i.e., slit nozzles) each of which comprises left and right portions.
Document 2 has disclosed that a predetermined thickness profile is formed in the ends of a coating film within a short range without non-uniformity by using two application dies (i.e., slit nozzles) each of which comprises left and right portions and has a slit of a width different from that of the other die. By using such two dies, the position where the coating liquid is applied is displaced with respect to the width direction, and the applied area becomes different. As a result of this, it is possible to form a desired thickness profile with respect to the width direction.
Document 3 has disclosed that a coating liquid is applied to an object to be coated by using two dies at the same time, each of which comprises left and right portions, in a state where the coating liquid ejected from a coating apparatus is not layered on the object to be coated.
[Document 1] Japanese Patent No. 3236703 (pages 4-6, FIG. 9)
[Document 2] Japanese Patent Application Publication No. 2000-102759 (pages 5-10, FIG. 4)
[Document 3] Japanese Patent Application Publication No. 2001-907 (pages 4-8, FIG. 2)
However, in the conventional art, it is necessary to perform accurate processing to hard metal such as stainless steel or SUS in order to manufacture a slit nozzle because the ejection opening and the ejection width of the slit nozzle needs to be very precise. It takes a lot of time and labor to perform such accurate processing, and also it is expensive.
In addition, even if accuracy of the processing is improved as much as possible, a very small gap is generated partly in the boundary of the two portions of the slit nozzle due to the large width of the slit nozzle, in which capillary action occurs and the treatment liquid soaks therethrough. This small volume of treatment liquid becomes a particle or the like when it is dried and/or cured.
The present invention was made to solve the above-mentioned problems, and the object of the present invention is to provide a slit nozzle and an apparatus for supplying a treatment liquid using the slit nozzle in which processing to a slit nozzle is easy, and no capillary action occurs.